Flow injection atomic absorption spectrometric determination of iodide using an on-line preconcentration technique

A continuous Row atomic absorption spectrometric system was used to develop an efficient on-line preconcentration-elution procedure for the determinat ion of iodide traces. Chromium (VI) is introduced into the flow system and is reduced to chromium (III) in acid medium proportionally to the iodide pr esent in the sample. The Cr(III) reduced by iodide is retained on a minicol umn packed with a poly(aminophosphonic acid) chelating resin, while unreduc ed Cr(VI) is not retained. Reduced Cr(III) is preconcentrated by passing th e sample containing iodide through the system during 3 min, and is then elu ted with 0.5 mol L-1 hydrochloric acid and determined by flame atomic absor ption spectrometry (FAAS). The detection limit (3 sigma) obtained is 2.5 mu g L-1. Other ions typically present in waters do not interfere. The propos ed method allows the determination of iodide in the range 6-220 mu g L-1 wi th a relative standard deviation of 2.7% at a rate of 17 samples h(-1). The method has been applied to the determination of iodide in tap and sea wate rs.